1. Field of the Invention
The present invention relates to a touch display panel and, more particularly, to an organic light emitting diode (OLED) display panel with touch sensing electrodes.
2. Description of Related Art
In recent year, the flat panel display industry has been rapidly developed, and many products have also been made in pursuit of light weight, thinness, small volume and fine image quality for developing several types of flat panel displays to replace traditional cathode ray tube display (CRT). The flat panel display includes liquid crystal display (LCD), plasma display panel (PDP), organic light emitting diode (OLED) display, field emission display (FED), and vacuum fluorescence display (VFD).
Among these types of flat panel displays, the OLED display technology is the one with great potential. OLED was first published by Eastman Kodak Co. in 1987. It has the features of thinness, light weight, self-illumination, low driving voltage, high efficiency, high contrast, high color saturation, fast response, flexibility, etc., and is therefore deemed as positively evaluated display technology following the TFT-LCD. In recent years, due to the development of mobile communications, digital products and digital televisions, the demand for high-quality full-color flat panel displays is rapidly increased. The OLED display is provided with not only the advantages of LCD display including thinness, power-saving, and full-color display, but also the features of wide viewing angle, self-illumination, and fast response that are better than LCD.
Modern consumer electronic apparatuses are typically equipped with touch panels for use as their input devices. The principle of touch panels is based on different sensing manners to detect a voltage, current, acoustic wave, or infrared to thereby detect the coordinates of touch points on a screen where a finger or touch pen touches. For example, a capacitive touch panel uses a capacitance change generated in an electrostatic combination of the arranged transparent electrodes with a human body to generate a current or voltage for detecting touch coordinates. With the widespread use of smart phones, the multi-touch technique is getting more and more important. Currently, the multi-touch is typically implemented by projected capacitive touch technique.
The projected capacitive touch technique can be divided into the mutual-capacitance touch sensing technique and the self-capacitance touch sensing technique. FIG. 1 schematically illustrates the transparent electrode structure of a single-layer touch panel of the self-capacitance touch sensing technique. As shown, there are a plurality of transparent electrodes 11 arranged in rows and columns, and the electrical signal sensed by one transparent electrode 11 is transmitted through a corresponding conductive wire 12 for output. Such a single-layer transparent electrode structure can realize an actual multi-touch detection. In use, the single-layer transparent electrode structure of FIG. 1 is combined with a display panel. However, when the single-layer transparent electrode structure is integrated to the inside of a display panel, there will be an obvious capacitance produced between the single-layer transparent electrode structure and a common voltage (Vcom) layer of the display panel, which may cause noises to be produced and thus lower the accuracy in detection the touch position. Therefore, it is known that the touch control circuit, particularly the touch control circuit of the in-cell touch panel, is highly susceptible to noises. The conductive wire 12 is used to transmit the electrical signal sensed by the transparent electrode 11, and thus the area of the conductive wire 12 cannot be used to sense the variation of capacitance, resulting in a dead area for the touch detection. Moreover, the common voltage (Vcom) layer of the display panel will form a shielding layer for external object, i.e. the user's finger, and it is difficult to integrate the in-cell self-capacitance touch sensing technique into the OLED display.
Therefore, it is desirable to provide an OLED display panel with touch sensing electrodes to mitigate and/or obviate the aforementioned problems.